Passenger vehicles having convertible tops that can be raised to cover the passenger compartment and lowered to open the compartment predate the closed sedan type of vehicle and have been manufactured for many years. Recently, vehicles having convertible tops have become more popular with purchasers because of their ability to quickly convert from a closed vehicle to an open roadster by lowering the top. Consequently, automobile manufacturers are manufacturing a greater variety of these sporty vehicles.
The usual convertible top comprises an articulated top frame that supports a fabric cover. The frame includes a plurality of spaced transverse bows interconnecting articulated side rails that support the fabric cover. The rear of the cover is attached to the vehicle body or, in some cases, to a movable rear bow, as illustrated in U.S. Pat. No. 5,067,768 to Roderick C. Fischbach and assigned to the assignee herein. The front edge of the cover is attached to the front bow, called the top header.
The top header engages the top of the vehicle windshield frame, or windshield header, in top raised position. Header latches, such as shown in U.S. Pat. 4,741,571 to Godette, clamp the headers together and compress a seal between them. Upon releasing the latching mechanism, the top is folded and lowered into a well located behind the passenger compartment. This action may be accomplished manually or by a power operator, usually a pair of hydraulic cylinders.
The top is raised by reversing this procedure, with switch actuation causing the hydraulic cylinders to raise and unfold the top until the top header is in close proximity to the windshield header. The latches are then manually engaged and operated to compress the seal and secure the headers together. One requirement of all convertible vehicles is that the top cover fit snugly on the frame so as to present a smooth, sleek appearance. This snug fit also reduces the vehicle's coefficient of drag, which affects gasoline mileage--a critical vehicle attribute. A snug fit is accomplished by stretching the cover taut over the frame. Cover stretching occurs at the end of the top raising cycle by fully extending the top frame and operating the header latches.
In a power-operated top, a switch is manually operated to actuate the power operator to raise the top. When a power-operated top is fully raised, the fabric cover is stretched when the hydraulic cylinders fully extend the frame linkage to move the top header into close proximity to the windshield header at the end of the cycle. When the power operator is turned off by releasing the manual actuation switch, hydraulic pressure quickly diminishes in the cylinders and the top "springs back" as the stretched fabric contracts, moving the headers apart. The top header must then be manually forced down onto the windshield header to enable the latches to be engaged and closed. Since this action again stretches the fabric cover, it requires a significant amount of manual effort.
This problem is exacerbated during cooler weather when the top fabric stiffens, requiring increased effort to manually stretch the cover fabric to engage the headers, followed by added effort to close the latches. The added manual effort required to accomplish top latching can be quite aggravating to the vehicle owner.
Although power latches have been devised, they are expensive and complex. Consequently, most convertible tops feature manual latches, the operation of which are plagued by the problem described above.
As a styling feature, it is desirable to have the top stored invisibly. Thus the top must store as fully within the well as possible. It is also desirable to store the top in as little space as possible, since the well volume subtracts from the vehicle's luggage capacity. As a result, the well is minimally dimensioned and the top is designed to fold into a compact package, with the tonneau fitting tightly over the stored top.
When the top is lowered, the power operator compresses the linkage and the folded fabric cover. When the power is turned off upon release of the switch, the top will "spring up" due to the elasticity of the top linkage and cover. This necessitates the use of additional manual effort to recompress the top and install the tonneau over the stored top. This problem is also exacerbated by cold weather, when the fabric cover stiffens.
It is quite desirable to reduce the manual effort required to latch a convertible top header to a windshield header.
It is also desirable to reduce the effort required to install a tonneau over a stored convertible top.